Optical spectrometers allow the study of a large variety of samples over a wide range of wavelengths. Materials can be studied in the solid, liquid, or gas phase either in a pure form or in mixtures. Various designs allow the study of spectra as a function of temperature, pressure, and external magnetic fields.
Near-Infrared (NIR) spectroscopy is one of the most rapidly growing methodologies in product analysis and quality control. In particular, NIR is being increasingly used as an inspection method during the packaging process of pharmaceuticals or food products. More and more often, this technique is augmenting or even replacing previously used vision inspection systems. For example, an NIR inspection system can be used to inspect a pharmaceutical blister package (such as an oral contraceptive or allergy medication) for, among other things, physical aberrations, chemical composition, moisture content, and proper package arrangement.
Most notably, NIR spectrometry inspection systems can be used to evaluate the chemical composition of products during the packaging process. Particularly with solid dosage pharmaceutical products, a group or package of products may look identical in the visible portion of the spectrum but may have unique chemical signatures in the near-infrared range (e.g. the 800-2500 nm range). Variations in the chemical composition of a tablet or capsule are usually grounds for rejecting a package containing a tablet with such a discrepancy. In operation on a pharmaceutical blister packaging machine, a still uncovered blister pack containing tablets or capsules passes an inspection station where it is examined. Once the inspection device inspects the blister pack to ensure that the correct material is located in each of the tablet or capsule wells, the packaging machine seals the blister pack. Those packages that fail the inspection process are rejected at a subsequent station. Subject to regulatory requirements, the rejected tablets may also be recycled for further processing.
The use of vision systems as an inspection mechanism continues to become less desirable as the need for more in depth inspection procedures and near 100% inspection processes are desired. Of particular concern is that known vision systems are inherently incapable of performing a chemical analysis of the product being packaged. Rather, vision systems rely solely on a comparison of a visual snapshot of the package to a previously stored reference image. Known vision packaging inspection systems “look” at each individual package to see whether it has the correct number of doses in the pack. For example, vision systems look for missing or overfilled tablet wells. In some cases, physical discrepancies, cracks, or gouges on a tablet will also cause a vision system to reject the package. What may not be detected by a vision system is the situation where each of the products in a package appears to be similar and in conformance with a reference image but the formulation of one or more products within the package are incorrect, or the wrong product composition is inserted into the packaging. The limitations of these types of known visions systems become readily apparent when higher levels of inspection are required and when they are compared with the expanded capabilities of a spectrometer-based inspection system.
Even though spectrometer-based monitoring and inspection systems are becoming more prevalent, many of them still have limited capabilities. These limitations are primarily due to the requirement that each tablet or capsule in a package be independently inspected by the spectrometer system. Therefore, a conventional spectrometer can only look at and analyze one sample at a time. Thus, the larger the number of products that are being inspected, the longer it will take to perform the inspection. Adding additional spectrometers is not a preferred solution because of the costs and maintenance issues associated with the increased hardware. Since spectrometer-based systems are meant in large part to replace vision systems, both accuracy and speed remain important factors when utilizing such systems. Thus, it would be desirable to have a spectrometer-based inspection system that can maintain the throughput of traditional vision systems without sacrificing the ability to perform accurate chemical composition analysis and without requiring the addition of expensive and problem prone equipment.
In many cases, multiple formulations are packaged into a single blister pack. Therefore, it is also desirable to have a spectrometer-based inspection system that can detect when an item is in the wrong location within the larger package that is being inspected while at the same time realizing the benefits of a spectrometer based inspection system.
Finally, it is desirable to have a spectrometer-based inspection system that can execute a self-referencing calibration in order to obtain conforming data to compare with during an inspection process as well as to determine item locations from a previously unknown package layout.